Hydrocarbon conversion process using catalysts having metals deposited on siliceous supports



United States Patent HYDROCARBON CONVERSION PROCESS USING CATALYSTSHAVING METALS DEPOSITED 0N SILICEOUS SUPPORTS Bernard F. Mulaskey,Pinole, Califi, assignor to Chevron Research Company, San Francisco,Calif., a corporation of Delaware No Drawing. Filed Jan. 24, 1966, Ser.No. 522,344

7 Claims. (Cl. 208-111) This application is a continuation-in-part of mycopending application Ser. No. 192,356, filed May 4, 1962, nowabandoned.

This invention relates to processes for converting hydrocarbons inhydrocarbon fractions to lower boiling hydrocarbons by contacting withhydrogen and catalysts. More particularly, the invention relates to suchprocesses using novel catalysts comprising metals which form amminecomplexes, or which are soluble in ammonium hydroxide solutions,deposited on silica-containing carriers.

Metals or metal compounds are commonly deposited on refractory oxidesupports or carriers as a means of preparing solid catalysts. The mostwidely used method is impregnation. In the impregnation technique, themetal concentration in the final catalyst is fixed predominantly by themetal concentration in the impregnating solution and by the pore volumeof the carrier. The mechanism is substantially the same whether an acid,neutral, or basic aqueous impregnating solution or a nonaqueous solutionis used. The impregnating solution is physically adsorbed in the poresof the carrier, which may be natural or synthetic silica, alumina,magnesia, titania, zirconia, natural earths and clays, etc., or mixturesor compounds of two or more of the foregoing. The pores of suchmaterials have been pictured as analogous to small channels orcapillaries; but when the carrier is amorphous, probably the pore volumeis actually a measure of the volume of interstices between the minuteparticles of the amorphous materials. If the carrier is crystalline, asin the case of crystalline alumino-silicate zeolites, the pore volumeincludes space within the three-dimensional cage structure or network ofthese so-called molecular sieves, and also interstitial space betweenthe usually minute crystals if they have been compacted or otherwiseformed into larger particle agglomerates, for example using amorphoussilica-alumina gel as a binder. Whatever the nature of the pores, whenthe excess impregnating solution is drained from the carrier, and thecarrier then dried and/ or calcined, the liquid trapped within the poresevaporates leaving the metals impregnated therein. Prior to calcining,the impregnating solution in the pores can be washed out or displaced,for example, by water. After calcining, some of the impregnated metal istightly bound to the carrier, but most of it is on the surface andreadily extractible by chemical means without affecting the carrier.

The conversion process of this invention comprises contacting ahydrocarbon fraction at a temperature in the range of 400900 F. and apressure in the range of 500-5000 -p.s.i.g. with hydrogen and certainnovel catalyst compositions consisting essentially of asilica-containing mixed-oxides carrier having a hydrogenation promotingmetal component deposited thereon by chemisorption as describedhereinafter. The novel catalysts are particularly active in convertinghydrocarbons contained in the hydrocarbon fraction to lower boilinghydrocarbons by the action of hydrogen at the named conditions, i.e. forhydrogenating and hydrocracking. The hydrocarbon fraction may be animpure raw oil such as a straight run petroleum distillate, or it may bea fraction resulting from previous cracking or other conversion ofpetroleum or Patented June 27, 1967 'ice similar material or fractionsthereof. In some cases it is desirable to eliminate contaminants such assulfur and nitrogen compounds from the hydrocarbon fraction feed to theprocess, but this is not always essential. The contacting may be done bypassing the hydrocarbon fraction and hydrogen at reaction conditionsthrough one or more beds of catalyst particles in a reaction vessel, orvarious other well known contacting techniques may be used.

The process of this invention uses catalysts prepared by a novel methodto deposit a hydrogenation promoting metal on a silica-containingcarrier in a form more tightly bound to the carrier and less extractiblethan impreg nated metal. The method of depositing the metal component,in accordance with one embodiment of the invention, compriseschemisorbing the maxi-mum amount of the metal preferentially on thesilica portion of the siliceous mixed-oxides carrier by contacting saidcarrier with a solution of an ammine complex of the metal inconcentrated aqueous ammonia. It has been discovered that metal-amminecomplexes in concentrated aqueous ammonia solution apparently chemisorbonly on silica or on the silica portion of a silica-containingmixed-oxides carrier. This is surprising, because the silica is not anacidic-reacting material, and it would not be expected to have anyspecial afiinity for the metal-ammine complex. It has also been foundthat no more than a certain maximum amount of ammine complex of a givenmetal can be chemisorbed on a given siliceous carrier. The capacity of acarrier to chemisorb a particular metal-ammine complex is a property ofthe particular carrier, and it may be afiected by the method of in theintensity of the color, if the solution is not too concentrated. When nofurther color change is evident, chemisorption is consideredsubstantially complete. If the metal-ammine complex solution is notcolored, the progress of chemisorption can be followed by analyzingperiodically the solution in contact with the carrier.

In the past, catalysts have been prepared by impregnation of amorphouscarriers with an ammoniacal solution of a metal. A small amount ofchemisorption, only about one-fourth or less of capacity, inherentlyaccompanied such impregnation of carriers containing silica, but thephenomenon was not recognized as taking place. Because chemisorption wasnot appreciable, it was not realized that the chemisorbed metal ispreferentially on the silica and more tightly bound to the carrier thanthe impregnated metal. Hence, there was no attempt either tosubstantially satisfy the chemisorption capacity of the carrier or todeposit the metal only by chemisorption to the exclusion of impregnationor precipitation.

Also, catalysts have been prepared by treating crystalline aluminosilicate zeolites with metal-ammine complexes in ammonia-free solutionsat conditions for dis placing or ion-exchanging cations in the zeolitelattice with the metal-ammine complex cations. These methods eitherexclude the presence of metal promoter in any position other than as anexchanged cation, or else Permit the usual impregnation-pmcipitation tooccur as well.

In the new method the carrier is contacted with the ammoniacalmetal-containing solution at conditions for maximum chemisorption withminimal deposition of metal by precipitation, impregnation, or ionexchange. The principal conditions to be considered are carrier particlesize, metal concentration in the solution, and time.

For maximum chemisorption of the metal on the carrier, the carriershould be in the form of particles smaller than about 14 mesh,preferably smaller than 100 mesh, especially in the form of fine powder.Maximum chemisorption is not readily achieved with larger particles suchas pellets, because the solution diffusing into the pellets isprogressively depleted in metal content. Hence, an inordinately longcontact time would be required, or a very concentrated solution wouldhave to be used, or the concentration of chemisorbed metal would be lessat the inside than on the outside of the pellet. After depositing themetal on the small carrier particles in accordance with the invention,the resulting composite may then be formed into larger shaped particlessuch as pellets or extrusions, if desired.

The carrier on which the metal component is to be deposited is a solidrefractory oxide containing silica, desirably a high-area, microporous,material. The carrier will contain other components in addition tosilica, such as alumina, titania, zirconia, and/ or magnesia, but thesilica portion should be substantial, usually at least about 25% of thetotal. Highly useful catalytic materials are prepared using as thesupport an amorphous silica-alumina carrier containing above 25% and upto 90% silica, for example, a silica-alumina cogel. Superior catalystscan be prepared using crystalline alumino-silicate zeolites containing40-80% silica as the carrier for certain hydrogenation promoting metalcomponents.

The metal to be deposited on the carrier must be one which is capable offorming an ammine complex in concentrated aqueous ammonia solution, orwhich is soluble in ammonium hydroxide and forms an insoluble silicate.Metals known to form such complexes readily are cobalt, nickel, copper,gold, and silver. Other metals exhibiting this property to a lesserextent include iron, magnesium, zinc, cadmium, strontium, cerium,thorium, and the platihum-palladium group metals. The metal should notform a salt with ammonia.

The solution of metal-ammine complex is best formed by dissolving anacidic salt, such as the nitrate, chloride, carbonate, acetate, etc., ofthe metal in concentrated aqueous ammonia. After 3 to 6 mols of ammoniaper mol of metal are required to form the complex. Also, excess ammoniais desirably present. Hence, the solution of metal-ammine complex willhave a pH of at least 10, and usually of about 13. The solution can berelatively dilute with respect to metal concentration, preferably lessthan about 1 molar. Nevertheless, high metal concentrations on thecarrier can be achieved because the amount of metal chemisorbed isdetermined by the chemisorption capacity of the carrier for theparticular metal, rather than by the solution concentration. The abilityto use dilute solutions makes the method particularly advantageous todeposit metals which are only slightly soluble.

An ammine complex may also form in nonaqueous or nonammoniacalsolutions. However, it is important for the chemisorption of theinvention that both the ammine and the solution be strongly basic andionic. Hence, solutions other than aqueous ammonia are of limitedapplicability. The ionic strength may be increased by includingnonmetallic ammonium salts, such as carbonates, halides, etc., in thesolution. The solution may be kept saturated with ammonia by bubbling NHgas through it. In the examples hereinafter where reference is made toconcentrated aqua ammonia, this was the reagent grade 28-30% NHsolution.

In contrast to the physical adsorption occurring in the usualimpregnation techniques, which is quite rapid and usually completedwithin a few minutes, the chemisorption ocurring in the preparation ofcatalysts for this invention is relatively slow. The contact timerequired between the siliceous carrier and the ammoniacal solution formaximum chemisorption depends to some extent on the size of the carrierparticles, the concentration of metal in the aqueous ammoniacalsolution, and the metal concentration desired on the carrier.Chemisorption may be nearly completed within 30 minutes in the case of apowdered carrier and a reasonably concentrated solution. Usually about 2hours or longer is required. In general, the chemisorption will becompleted within 24 hours, though longer contact times may be used.Unless superatmospheric pressure is imposed, the temperature duringchemisorption is preferably maintained near atmospheric conditions, toavoid loss of ammonia by evaporation, but warm enough for reasonablyrapid diffusion of metal to the carrier and chemisorption. When thecarrier is contacted with the ammoniacal metal solution at its boilingpoint, the metal does not chemisorb selectively. Thus, ordinary roomtemperature is desirable for process reasons as well as beingconvenient.

The amount of solution used need be only that amount which containsinitially in solution the amount of metal corresponding to thechemisorption capacity of the carrier, or less if a low metal contentcatalyst is desired. However, it is preferred to use excess solution inorder to reduce the contact time required. In the chemisorption method,the concentration of metal in the solution gradually declines asmetal-ammine complex is abstracted from the solution and chemisorbed onthe carrier. The final concentration of metal chemisorbed on the carrieris then fixed by the intrinsic properties of the support in terms ofchemisorption capacity, which is independent of the solutionconcentration above the minimum amount needed to provide the amount ofmetal desired to be deposited. That is to say, a fixed metalconcentration will be achieved provided that sufficient time is allowedfor completion of the chemisorption and provided that there issufiicient metal present in the amount of solution used. If less metalis present than the chemisorption capacity of the carrier, the solutionwill be depleted of metal.

As previously mentioned, the time of contact for maximum chemisorptionis relatively long. In impregnation, the ultimate maximum metalconcentration is achieved in contact times between the carrier and thesolution as short as a few minutes, and rarely over 15 minutes isrequired. If the carrier is withdrawn from the aqueous ammoniacalsolution of metal-ammine complex before more than about 15 minutes ofcontacting, the amount of metal deposited is found to be only a littlemore than that which would be obtained by impregnation. If, however, thesolution is allowed to contact the carrier particles for a much longertime, preferably about two hours or longer, a much higher metalconcentration is achieved.

It is quite apparent that both chemisorption and impregnation can takeplace during contacting of the carrier with the solution, except in thesituation where only suflicient metal is provided in the originalsolution to satisfy the chemisorption capacity. Thus, if excess solutionis used, or if the solution is more concentrated than necessary, afterthe carrier has chemisorbed the metal up to its capacity, there willstill be metal-containing solution adsorbed in the pores. Hence, whenthis impregnated material is dried, the total metal concentration of thecarrier will be higher, equal to the sum of chemisorbed and theimpregnated metal.

In the preferred catalysts for the conversion process of this invention,chemisorption predominates. It is especially desired that the metalcomponent be deposited essentially by chemisorption, which is consideredto be the case when the weight of metal deposited on the carrier is atleast three times the weight of metal which would be deposited thereonif the support were impregnated with a nonammoniacal solution of thesame metal concento deposit cobalt on a pulverized silica gel carried byimpregnation and by chemisorption. The data obtained, presented in thefollowing Table III, again show that there is a constant differencebetween the metal content of the chemisorbed catalyst and that of theimpregnated catalyst, in this case about 4-5 weight percent,representing the chemisorption capacity of the carrier. Up to a solutionconcentration of 0.5 molar, the weight of metal deposited on the carrierby the chemisorption method is over three times the weight of metaldeposited on the carrier by impregnation with an aqueous solution of thesame metal concentration.

TAB LE III Wt. Percent Cobalt on Silica Gel Cobalt Acetate in Solution,Mols/Liter Impregnation with Chemisorption from Distilled WaterAmmoniacal Solution Solution An 86% silica-14% alumina cogel crackingcatalyst in the form of 10-28 mesh particles was contacted for severaldays with a dilute solution of nickel carbonate (about .05 molar) inconcentrated (saturated) ammonium hydroxide. The contactedsilica-alumina was drained free of excess solution, dried, heat treatedat 1400 F. for two and one-half hours, reduced two hours at 800 F. inhydrogen, and sulfided for two hours at 600 F. in H S. The catalystcontained 5.24% nickel. Only 0.5% nickel, or less, would be obtained byimpregnating with a nonammoniacal solution of the same nickel content.Normal decane was passed over this 5.24% Ni catalyst, sulfided in alaboratory reactor at a rate of 16 volumes of decane per volume ofcatalyst per hour, at 1200 p.s.i.g., 500 F., with hydrogen in amol/ratio of hydrogen to n-decane of 10 to l. The n-decane washydrocracked to lower boiling products to the extent of 5.1 weightpercent, which indicates a good hydrocracking activity, in view of thehigh space velocity and low temperature used.

Example 5 A 5 gram sample of commercial synthetic crystalline sodiumalumino-silicate zeolite, designated Zeolite 13X by the supplier, LindeCo., with the approximate composition Na O-Al O -2SiO and in the form ofparticles crushed to about 20 mesh or smaller, was immersed in 200 ml.of concentrated aqueous ammonia containing nickel acetate at 0.05 molarconcentration .and allowed to stand at room temperature with occasionalstirring, for one day. The particles were then filtered from thesolution, dried and calcined, and analyzed and found to contain 2.35 wt.percent nickel. In the same way, aluminosilicate based catalystscontaining, respectively, 3.24 wt. percent cobalt, 4.13 wt. percentcopper, 7.55 wt. percent silver, were prepared. These catalysts are alluseful in hydrocracking hydrocarbons, though the copper and silvercatalysts are less active than the cobalt and nickel, and the latter areless active than many similar catalysts prepared on amorphoussilica-alumina carriers. The relatively lower activity is attributableto the sodium present in'the zeolite, as alkali metals are notoriousoffenders in adversely affecting cracking reactions.

Example 6 Palladium chloride, about 10 grams, was dissolved in about 3/2 liters of concentrated (28-30%) aqua ammonia at room temperature,giving about a 0.015 molar metal solution. To this was added 1 pound ofsynthetic alumino-silicate zeolite crystals essentially free of alkalimetal and alkaline earth metal cations, designated decationized ammoniaY sieve by the supplier, Linde Co., having the approximate compositionAl O -5SiO -YH O and in the form of a crystal powder smaller than mesh,and the mixture was allowed to stand 2-3 days at room temperature withoccasional stirring. The one pound of molecular sieve is on a dry basis,the material as obtained containing about 30-40% water of hydration. Thecrystals were filtered from the supernatant solution, dried at F.,tabletted, crushed to 8-14 mesh, and calcined 2 hours at 1000 F. Thefinished catalyst, analyzing 1.22% Pd, was tested for hydrocrackingactivity, by contacting a partially hydrofined catalytic cycle oil,400-700 F. boiling range, containing 20 ppm. organic N and 0.3 wt.percent sulfur, at 1600 p.s.i.g. with 12,000 s.c.f. of hydrogen. At 625F., conversion to lower boiling hydrocarbons, C 400 F., was 60%.

In the above Example 6 the metal-ammonia solution was so dilute withrespect to metal content that the chemisorption capacity of the carrierwas not satisfied, the solution being depleted of metal. In other testsit was shown that the Pd content of the catalyst could be adjusted in arange up to 4% Pd by using a more concentrated metal solution.

A catalyst prepared similarly in accordance with Example 6, containing2% platinum instead of palladium, had slightly better activity than the1% Pd catalyst. Thus, the chemisorption capacity of the carrier for themetal need not be completely satisfied to provide an effective catalyst,provided the metal present is deposited predominantly by chemisorption.

Example 7 Cobalt chloride hexahydrate, 198 g., was dissolved in about 3/2 liters of concentrated aqua ammonia, and one pound (dry basis) of theammonia-Y sieve described previously was added. The solution thus wasabout 0.24 molar in cobalt concentration. Following the same proceduresof letting stand, filtering, etc., and calcining as in Example 6, therewas produced a catalyst containing 6.85% Co which had good hydrocrackingactivity and stability when sulfided. In this case the chemisorptioncapacity of the carrier was satisfied, and the ammoniacal solution usedin the preparation still contained cobalt.

The following example shows that the metal deposited by chemisorption isattached to the carrier more tightly and in a different manner than thatdeposited by impregnation, whereby the chemisorbed metal is lessextractible.

Example 8 It has been found that a portion of the nickel oxide on acalcined impregnated catalyst can be extracted by complexing it withdimethylglyoxime and dissolving the resulting nickel complex in anorganic solvent. Sulfiding makes the nickel more extractible. A weighedamount of the catalyst powder is dropped into a large volume of a 50:50mixture of absolute alcohol and chloroform con taining dimethylglyoxime.The catalyst is allowed to stand in contact with the solution for oneday. The amount of nickel extracted is then determined by measuring theoptical transmission of the solution. From a calcined 5.4%nickel-on-silica-alumina catalyst prepared by the usual impregnationtechnique, 100 micromols of nickel per gram were extracted in thismanner. From a calcined 5.24% nickel catalyst prepared by chemisorbingnickel ammonium carbonate on silica-alumina, as in Example 4, only 15micromols of nickel per gram were extractible. Sambut the chemisorptionmethod produced very high metal concentrations. In the case of the 86%silica-14% alumina, very little metal was deposited by the impregnationtechnique, but the chemisorption method again gave high metalconcentrations. The excess solutions were also analyzed, and in thecases of chemisorption on silical gel and silica-alumina were found tobe reduced in metal content.

TABLE I Weight Percent Metal on Alumina Weight Percent Metal on SilicaGel Weight Percent Metal on 86% Silica, 14% Alumina Metal SolutionCopper Nickel Silver Cobalt Distilled Water 0. R6 0, 5'5 Nil AqueousAmmonia 0. 95 8S 0. 54 7. 06

Copper Nickel Silver Cobalt Copper Nickel Silver 095 Nil 0.35 0.57 0.358. 26 5. 58 8. 62 4. 42 6. 04 3. 55 7. 55

must be used in order to obtain at least three times the metal contenton the carrier as would be obtained by impregnation with a solution ofthat same metal concentration. Otherwise, a large amount of impregnationwould occur along with the chemisorption.

The metal can be deposited preferentially on the silica by chemisorptioneven if a more concentrated metal ammine solution is used, Thus, anyexcess impregnating solution within the pores may be washed out, as bydisplacing with distilled water, prior to drying and calcining theparticles. The chemisorbed metal is not removed by this treatmentbecause it is tightly bound to the carrier. Additional metal, forexample, a different metal, may then be deposited by impregnation orotherwise on the metalcontaining particles prepared by thischemisorption technique, preferably after fixing the metal by drying andcalcining. In particular, in the case of a silica-alumina carrier,additional metal may be deposited preferentially on the alumina portionby adsorption from an aqueous metal fluoride solution, by the methoddisclosed in US. Patent No. 3,140,925 to R. H. Lindquist and R. 0.Billman. Different results are obtained by this method, as compared tothe results obtained when excess impregnating solution is not washedoif, because the chemisorption itself often causes changes in thestructure of the carrier with respect to decreasing surface area,increasing pore volume, and expanding pore diameters, for example. Theextent of such changes can be controlled by adjusting the metalconcentration in the solution and consequently the time required forchemisorption. By thus depositing a metal by chemisorption only on thesilica portion of a mixed-oxides carrier, thereby altering theproperties of the carrier, and then depositing additional metal,catalysts having new and novel properties can be prepared.

The following example demonstrates that the chemisorption describedherein takes place only on silica or on the silica portion of amixed-oxides carrier, and does not occur to any noticeable extent on analumina carrier.

Example I Metals were deposited on three carriers, a powdered alumina, apowdered silica gel, and a powdered 86% silical4% alumina, by twoprocedures. In one case the carriers were impregnated by immersing 5grams of the carrier in 200 cc. of solution of the metal acetate indistilled water, which had a concentration of 0.05 molar with respect tothe metal. In the other case, for chemisorption, 5 grams of each carrierwere immersed in 200 cc. of 0.05 molar solution of the metal acetate inconcentrated (30%) ammonium hydroxide. The carriers were allowed tostand in contact with the solutions for one day. The carriers were thenwithdrawn from the solutions, dried and calcined, and then analyzed formetal content. As shown in the following Table I, which presents thedata obtained, very little metal was deposited on the alumina by eitherimpregnation or by chemisorption, using these dilute solutions. Verylittle metal was deposited on the silica gel by the impregnationtechnique,

Thus, it is apparent that the chemisorption method deposits the metalpreferentially on the silica portion of the carrier. Also, much highermetal concentrations are obtained on silica-containing carriers by thischemisorption method as compared to impregnation techniques, using verydilute solutions.

The following Examples 2 and 3 further illustrate the higher metalconcentrations obtainable by the chemisorption method, and show that incontrast to impregnation, where the metal concentration on the carrieris proportional to the concentration of metal in the solution, inchemisorption the metal concentration achieved is primarily a propertyof the carrier.

Example 2 Solutions of varying concentrations of nickel nitrate wereprepared both in distilled water (for impregnation) and in concentratedaqueous ammonia (for chemisorption). Portions of 86% silica-14% aluminapulverized cracking catalyst were then contacted with the solution for24 hours, drained free of excess solution, dried, calcined, and analyzedfor metal content. The data obtained, presented in Table II, show thathigh metal concentrations are obtainable by the chemisorption method,even with very dilute solutions. At a solution concentration below about1 molar, the quantity of metal deposited on the support is more thanthree times that which is deposited by impregnation using an aqueoussolution of the 88.1116 metal concentration.

TABLE II Wt. Percent Nickel on 86% Silica, 14 a Alumina Nickel Nitratein Solution,

Mols/Liter impregnation with chemisorption from Distilled WaterAmmoniacal Solution Solution This is the chemisorption capacity of thecarrier. The

chemisorbed metal is more tightly bound to the support than theimpregnated metal, and it cannot be removed by mere water washing.

Example 3 In this example experiments were carried out in substantiallythe same manner as in the foregoing Example 2, except that solutions ofcobalt acetate in distilled water and in concentrated aqueous ammoniawere used ples of the catalysts were also sulfided and then subjected tothe extraction with dimethylglyoxime. From the impregnated catalyst 625micromols of nickel per gram were extracted, but only 160 micromols pergram could be extracted from the chemisorbed catalyst.

In the case of the chemisorbed catalyst, it is seen that the smallamount of extractible metal can be largely accounted for as due to thesmall amount of nickel impregnated nonselectively on the silica-alumina(about 0.5%), while the metal chemisorbed preferentially on the silicaportion (about 4.7%) is much less extractible. Thus, the silica-aluminacarrier on which nickel was deposited by chemisorption had about gramsof nickel not extractible with dimethylglyoxime per 100 grams of silicachemisorbed on the silica portion of the carrier, only about 0.5 gram ofnickel per 100 grams of alumina supported on the alumina portion.Independent of the relative amounts of silica and alumina in thecarrier, compositions can thus be prepared having 3-10 grams ofchemisorbed nickel per 100 grams of silica on the silica portion and notover 1 gram of nickel per 100 grams of alumina on the alumina portion.

To summarize, it has been shown that metals which form complexes withammonia deposit selectively on a siliceous mixed-oxides carrier when thecarrier is treated with a dilute solution of the metal in concentratedaqua ammonia at room temperature, such that the metal is more tightlybound to the carrier and less extractible than metal deposited byimpregnation. The resulting catalysts are active for hydrocracking oils,i.e. converting hydrocarbons in hydrocarbon fractions to lower boilinghydrocarbons in the presence of hydrogen, when there is so deposited ahydrogenation promoting metal component comprising nickel, cobalt, or anoble metal of the platinum-palladium group. The cobalt and nickelcatalysts are best used with the metals present as sulfides whereas theplatinum and palladium may remain as elemental metal during use.

I claim:

1. Method of converting hydrocarbons in a hydrocarbon fraction to lowerboiling hydrocarbons which comprises contacting said fraction at atemperature in the range of 400-900 F. and a pressure in the range of500- 5000 p.s.i.g. with hydrogen and a catalyst composition consistingessentially of a silica-containing mixed-oxides carrier, composed of atleast 25% silica and at least one other oxide selected from the groupconsisting of alumina, titania, zirconia, and magnesia, and having ahydrogenation promoting metal component deposited thereon by contactingparticles of said carrier smaller than 14 mesh with a dilute solution ofan ammine complex of the metal, less than one molar with respect tometal content, in concentrated aqueous ammonia at about room temperatureavoiding ammonia vaporization, for at least two hours until said carrierhas chemisorbed the maximum possible amount of said metal from saidsolution, separating said particles from contact with said solution, andthereafter drying and calcining the particles.

2. Method according to claim 1 wherein said mixedoxides carriercomprises a synthetic silica-alumina cracking catalyst.

3. Method according to claim 2 wherein said metal component is nickel orcobalt sulfide.

4. Method according to claim 2 wherein said metal component is a noblemetal of the platinum-palladium group.

5. Method according to claim 1 wherein said mixedoxides carriercomprises a crystalline alumino-silicate zeolite.

6. Method according to claim 5 wherein said metal component is nickel orcobalt sulfide.

7. Method according to claim 5 wherein said metal component is a noblemetal of the platinum-palladium group, and said crystallinealumino-silicate zeolite carrier contacted with said solution isessentially free of alkali metal and alkaline earth metal cations.

References Cited UNITED STATES PATENTS 2,777,805 1/1957 Le Francois eta1. 208139 3,135,682 6/1964 Mason et al. 208-111 3,226,339 12/1965Frilette et a1 208138 DELBERT E. GANTZ, Primary Examiner.

A. RIMENS, Assistant Examiner.

1. METHOD OF CONVERTING HYDROCARBONS IN A HYDROCARBON FRACTIN TO LOWERBOILING HYDROCARBONS WHICH COMPRISES CONTACTING SAID FRACTION AT ATEMPERATURE IN THE RANGE OF 400-900*F. AND A PRESSURE IN THE RANGE OF5005000 P.S.I.G. WITH HYDROGEN AND A CATALYST COMPOSITION CONSISTINGESSENTIALLY OF A SILICA-CONTAINING MIXED-OXIDES CARRIER, COMPOSED OF ATLEAST 25% SILICA AND AT LEAST ONE OTHER OXIDE SELECTED FROM THE GROUPCONSISTNG OF ALUMINA, TITANIA, ZIRCONIA, AND MAGNESIA, AND HAVING AHYDROGENATION PROMOTING METAL COMPONENT DEPOSITED THEREON BY CONTACTINGPARTICLES OF SAID CARRIER SMALLER THAN 14 MESH WITH A DILUTE SOLUTION OFAN AMMINE COMPLEX OF THE METAL, LESS THAN ONE MOLAR WITH RESPECT TOMETAL CONTENT IN CONCENTRATED AQUEOUS AMMONIA AT ABOUT ROOM TEMPERATUREAVOIDING AMMONIA VAPORIZATION, FOR AT LEAST TWO HOURS UNTIL SAID CARRIERHAS CHEMISORBED THE MAXIMUM POSSIBLE AMOUNT OF SAID METAL FROM SAIDSOLUTION, SEPARATING SAID PARTICLES FROM CONTACT WITH SAID SOLUTION, ANDTHEREAFTER DRYING AND CALCING THE PARTICLES.